| Molecularly imprinted polymers (MIPs) are chemically stable synthetic polymers. MIPs were prepared according to templates, possessing empty caves matching with the templates in size、sharp and functional groups and having highly specific recognition ability for target molecules or similar compounds. Magnetic material is a kind of function material, which can be separated easily by an external magnetic field. Magnetic molecularly imprinted polymers (MMIPs) prepared through the combining of the molecular imprinting technique with magnetic separation technique are new functional polymer materials, possessing the specific adsorption property of MIPs and the rapidly separation property of the magnetic marerial. In this paper, the MMIPs were prepared by two different methods and applied in selective separation and enrichment of trace pesticide in complex samples. The main contents and results are listed as follow:(1) The MMIPs were synthesized by surface-imprinted polymerization in polyethylene glycol solution, using chlorpyrifos as template, magnetic SiO2(Fe3O4@SiO2) as supporter, methacrylic acid (MAA) as functional monomer, and trimethylolpropane trimethacrylate (TRIM) as cross-linker, potassium persulfate as initiator. The morphology, composition, magnetic propertiy and functional groups of the MMIPs were characterized with scanning electron microscope (SEM), thermogravimetric analyzer (TGA), physical property measurement system (PPMS) and Fourier-transform infrared spectrometer (FTIR). The adsorption properties of the polymers were studied by isothermal absorption, kinetic absorption and selective absorption. Combining the prepared MMIPs and high performance liquid chromatography (HPLC) analyzed the chlorpyrifos in rice. The obtained limit of detection (LOD) of chlorpyrifos was0.0072μg/g, the relative standard deviations (RSDs) of intra-and inter-day ranged from2.4%to4.6%and3.5%to7.3%, respectively. The recoveries of chlorpyrifos at three different fortified concentrations (0.025,2.5, and5μg/g) were in the range of81.2%-92.1%. The method could eliminate matrix interference and simplify the process of sample pretreatment.(2) The MMIPs were synthesized in dimethyl sulfoxide solution, using cyhalothrin as templates, magnetic carbon nanotubes (MCNTs) as matrix, ethylene glycol dimethacrylate as cross-linker, azo-isobutyronitrile (AIBN) as initiator and polyvinylpyrrolidone as dispersant. The polymers were characterized with transmission electron microscopy (TEM), Brunauer-Emmett-Teller method (BET). PPMS and FTIR, respectively. The result showed that there were two kinds of binding sites existing in MMIPs by drawing isothermal absorption to discuss the type of adsorption. Dissociation constants and the maximum adsorption capacitiy were calculated by Scatchard analysis. Kinetic adsorption experiment confirmed that the polymers were well fitted to the second-order equation. The selective factor was calculated by selectivity experiment, the result indicated that MMIPs had the ablity of selective adsorption towards cyhalothrin and its structural analogs. Pyrethroid residues in fruit samples were extracted with acetonitrile. The extract was diluted with water to be used as adsorption solution. MMIPs were used as adsorbent to extract pyrethroids in solution and HPLC was used to quantitative analysis. The effects of extraction conditions including amount of MMIPs, shaking time, washing solvent, back-extraction solvent and times were investigated, the experiment programs were optimized. The results indicated that the method had the advantages of short sample preparation time, low consumption of solvent and little polymer dosage, the satisfying recovery and sensitivity could be obtained in practical application. |
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